Phase 2 Inlet manifold modifications required to fit StiV3 heads on a 2.5

Hi,
I could do with some help and advice . I'm planning on fitting the 2.5 engine fitted to my modified RB5 with Sti V3 heads as I understand these have a more agressive cam profile which helps gas flow.

I know the phase 2 inlet manifold fitted to the car have a different bolt arrangement to the heads so have purchased some adapters to allow these to fit . Think these are made by Carl Davey judging by the photos . So I can keep the Phase 2 inlet manifold and avoid issues with changing the idle control valve , throttle position sensor set up .

I've read that the phase 2 inlet manifold has to be cut and welded to shorten the distance between the inlet port runners by 12 to 14 mm

However I've also heard someone say the Ph2 manifold doesn't need chopping and welding and can be squeezed on .

Anyone done this modification and what were your experiences ?

John H

You can get adapter plates to fit late manifolds on early heads but can't think who duz them

Hi John did we speak on the phone the other day ?.
I used Carl davey ph2 inlet to ph 1 heads but you would need to shorten the inlet legs, even with the inlet convertors.
These are the ones i used.
I,ve also used v5/6 heads with ph2 inlet fitted to a v4, made an adaptor plate to fit the ph2 icv to connect the early one as its on the trottle body, would v5/6 sti heads not be an easyier option for you.

you can see the mod to the tb to connect the early icv, still have it somewhere it you want it.

Hi Drew,
you're right . I've been able to source some manifold adapter plates from API engines . They are second hand and look identical to the Carl Davey ones so were probably made by him .

Thanks,
John

Hi Maxboost ( Mark ? )

Thanks for the reply as well . Yes , It must have been you I was talking to the other day but I didn't know who Maxboost was then.

The reason I want to fit the Sti 3 heads is because I've been told they flow really well because of the cams fitted . So I bought some refurbished Sti 3 heads from Darren at DLM a while ago , was going to fit them to my 93 WRX 2.5 , but then the RB5 came along so I ended up buying that .

So , if possible I want to fit the Sti 3 heads I already have rather than Sti V5/6 heads . I know it makes life difficult but I've never done things the easy way !

Do I just need to source a version 2 inlet manifold and have the runners cut and shortened 12 to 14 mm now ?

Cheers,
John

Hi John,
Yeah
Buy inlet
Do the icv mod as previously discribed
Mount your coil pack
Think thats it.
By all means give me a bell if needed.

Mark.